In this paper, I investigate the array of visual imagery found in popular pamphlets and more scholarly tracts dealing with the comets of 1618. The illustrations include iconic or symbolic depictions; allegorical images and emblems; pictures of observed phenomena as seen by the naked eye or produced by an instrument; illustrations of a practical setup for observation or experiment; visual ways to map data; diagrams of a supposed underlying structure of observed phenomena; and mathematical diagrams illustrating geometrical relationships, methods, or proofs. Analysis of the images shows them to have had rhetorical, didactic, psychological, and commercial purposes. They aided authors in illustrating, organizing, creating, and communicating knowledge. They show a dynamic and complex relationship between popular culture and scholarly debates, natural experiences and world views, and astronomy, politics, and religion.